The present invention relates generally to optical semiconductor devices and more specifically to optical semiconductor devices including light reflectors.
Most optical electronic circuits use fiber-optic cables to channel light between communicating entities. As an interface to transmit/receive electronics, a fiber-optic cable may channel light to an optical semiconductor structure within a semiconductor device casing. The fiber-optic cable may enter the semiconductor device casing from the top (vertically) or from the side (laterally), although lateral entry is generally preferable since it requires less complex supporting structures for the fiber-optic cables. In addition, laterally-entering cables may use a smaller vertical profile than vertically-entering cables and are generally more mechanically stable than vertically-entering cables.
On the other hand, top-interfaced (or vertically-interfaced) optical semiconductor devices are generally easier and less costly to fabricate than laterally-interfaced optical semiconductor devices. Therefore, prior efforts have attempted to use reflection mechanisms to interface laterally-entering fiber-optic cables with vertically-illuminated optical semiconductor devices. However, the prior efforts have not provided a robust, cost-effective, and highly manufacturable vertically-illuminated optical semiconductor device that may be laterally interfaced.
For example, one prior effort included fabricating a vertically-illuminated optical semiconductor device on a first substrate and fabricating light reflectors on a second substrate. The second substrate was then flipped and mounted to the first substrate. However, such a construction had many problems. Not only was the fabrication process for the device complicated, but the fine structures had to be fabricated on separate substrates, aligned, and attached. The mechanical alignment process was subject to alignment errors and the stacked substrates also caused the resultant device to be bulky. In addition, valuable real-estate on the substrate was typically occupied by solder bumps.
Another prior effort fabricated a vertically-illuminated semiconductor structure and a separate base structure. Then the vertically-illuminated semiconductor was mounted to the base structure on its side using a submount. This solution was complicated to manufacture because it involved processing two separate substrates and coupling the substrates orthogonally. Electrically connecting the substrates was also difficult because most connecting apparatus are designed to connect substrates that have substantially parallel planes. In addition, the solution was also vertically bulky.
Yet another past device used fiber-optic cable polished at a 45-degree angle and coated with a reflective material so that light passed out of the cable at an angle. However this device required a cable manufacturing process external to the fabrication of the semiconductor device. Thus, this device potentially places the burden on the user of the semiconductor device to specially prepare and/or align the fiber-optic cables. In addition, this solution is highly dependent on precise and difficult to achieve alignment of the fiber-optic cable with the device.
Thus, a need has long existed for an optical semiconductor device that overcomes the disadvantages noted above and others previously experienced.
A preferred embodiment of the present invention provides an optical semiconductor device. The optical semiconductor device includes a top-interfaced optical semiconductor structure and a light reflector monolithic with the optical semiconductor structure. The light reflector is disposed to direct light between the optical fiber and the optical semiconductor structure. The optical semiconductor structure may be, for example, a top-illuminated PIN photodiode. The light reflector may then, for example, direct the horizontal interface light from the fiber to the top surface of the top-illuminated PIN photodiode.
Another preferred embodiment of the present invention provides a method for fabricating an optical semiconductor device. The method includes fabricating an optical semiconductor structure, which may, for example, result in a top-illuminated PIN photodiode. The method also includes fabricating a light reflector monolithic with the optical semiconductor structure. Fabricating a light reflector may, for example, fabricate a dielectric support structure monolithic with the optical semiconductor structure and fabricate a substantially quarter-spherical metallic reflective surface adjacent to the light reflector support structure. Fabricating the light reflector may include disposing and shaping the light reflector to direct light to the top surface of the optical semiconductor structure.